Function w4a16_gemm_n128_m128_bf16_ldb 

pub fn w4a16_gemm_n128_m128_bf16_ldb(
    gpu: &dyn GpuBackend,
    kernel: KernelHandle,
    input: DevicePtr,
    weight: &QuantizedWeight,
    output: DevicePtr,
    m: u32,
    n: u32,
    k: u32,
    ldb: u32,
    stream: u64,
) -> Result<()>

2026-09-25: w4a16_gemm_n128_m128_bf16 with an explicit transposed-B row stride, for the same reason as w4a16_gemm_n128_ldb. This is the launcher for the 9-parameter w4a16_gemm_t_m128_bf16_v2.